Mongo-dbx NPM | npm.io

mongo-dbx

Synchronous and Asynchronous access to the Mongo Database from Node.js.

Chris Munt cmunt@mgateway.com
22 June 2023, MGateway Ltd http://www.mgateway.com

Verified to work with Node.js v4 to v20.
Release Notes can be found at the end of this document.

Pre-requisites

mongo-dbx is a Node.js addon written in C++. It is distributed as C++ source code and the NPM installation procedure will expect a C++ compiler to be present on the target system.

Linux systems can use the freely available GNU C++ compiler (g++) which can be installed as follows.

Ubuntu:

   apt-get install g++

Red Hat and CentOS:

   yum install gcc-c++

Apple OS X can use the freely available Xcode development environment.

There are two options for Windows, both of which are free:

Microsoft Visual Studio Community: https://www.visualstudio.com/vs/community/
MinGW: http://www.mingw.org/

If the Windows machine is not set up for systems development, building native Addon modules for this platform from C++ source can be quite arduous. There is some helpful advice available at:

Compiling native Addon modules for Windows

Alternatively there are built Windows x64 binaries available from:

https://github.com/chrisemunt/mongo-dbx/blob/master/bin/winx64

Installing mongo-dbx

Assuming that Node.js is already installed and a C++ compiler is available to the installation process:

   npm install mongo-dbx

This command will create the mongo-dbx addon (mongo-dbx.node).

Documentation

Most mongo-dbx methods are capable of operating either synchronously or asynchronously. For an operation to complete asynchronously, simply supply a suitable callback as the last argument in the call.

The first step is to add mongo-dbx to your Node.js script

   var mongodb = require('mongo-dbx');

Create a Server Object

   var db = new mongodb.server();

Open a connection to the Server

Synchronous:

   var result = db.open({address: <address>, port: <port>});

Asynchronous:

   db.open({address: <address>, port: <port>}, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

If the operation is successful, the ok flag will be set to true. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

For example, create a server connection object to a local MongoDB installation listening on the default port (27017).

   var result = db.open({address: "localhost", port: 27017});

Close the connection to the Server

Synchronous:

   var result = db.close();

Asynchronous:

   db.close(callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

Insert a new Document

Synchronous:

   var result = db.insert(<database>.<collection>, <document>);

Asynchronous:

   db.insert(<database>.<collection>, <document>, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>,
      _id: <document id>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

If the operation is successful, the ok flag will be set to true and the document's unique ID returned. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

Example:

   var result = db.insert("company.employee", {emp_no: 1, name: "Chris Munt"});

Insert a set of new Documents

This method is the same as insert except that it will take an array of Documents for inserting.

Synchronous:

   var result = db.insert_batch(<database>.<collection>, [<document>, ...]);

Asynchronous:

   db.insert_batch(<database>.<collection>, [<document>, ...], callback(<error>, <result>));

Result Object (an array of document IDs or notification of errors):

   [
      {
         ok: <ok flag>,
         _id: <document id>
         [, ErrorMessage: <message>]
         [, ErrorCode: <code>]
      },
      ...
   ]

For each Document, if the operation is successful, the ok flag will be set to true and the document's unique ID returned. Otherwise, the ok flag will be set to false and error information will be returned in the ErrorMessage and ErrorCode fields.

Example:

   var result = db.insert_batch("company.employee", [{emp_no: 2, name: "Rob Tweed"},
                                                     {emp_no: 3, name: "John Smith"}]);

Update an existing Document

Synchronous:

   var result = db.update(<database>.<collection>, <old document>, <new document>);

Asynchronous:

   db.update(<database>.<collection>, <old document>, <new document>, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>,
      _id: <document id>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

Example:

   var result = db.update("company.employee", {emp_no: 3}, {emp_no: 3, name: "Jane Doe"});

Remove Document(s)

Synchronous:

   var result = db.remove(<database>.<collection>, <document>);

Asynchronous:

   db.remove(<database>.<collection>, <document>, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

Example (remove a specific Document):

   var result = db.remove("company.employee", {emp_no: 3});

Example (remove all Documents from the Collection):

   var result = db.remove("company.employee", {});

Retrieve Document(s)

Synchronous:

   var result = db.find(<database>.<collection>, <query>);

Asynchronous:

   db.find(<database>.<collection>, <query>, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>,
      data: <results>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

The results will be held in the data field.

Example (retrieve all Documents in the Collection):

   var result = db.find("company.employee", {});

Example (retrieve a specific Document from the Collection):

   var result = db.find("company.employee", {$query: {emp_no: 1}});

Example (return optimization information for a query):

   var result = db.find("company.employee", {$query: {emp_no: 1}, $explain: 1});

Create an Index for a Collection

Synchronous:

   var result = db.create_index(<database>.<collection>, <index atributes>,
                                <index name>, <index options>);

Asynchronous:

   db.create_index(<database>.<collection>, <index atributes>,
                   <index name>, <index options>, callback(<error>, <result>));

Result Object:

   {
      ok: <ok flag>
      [, ErrorMessage: <message>]
      [, ErrorCode: <code>]
   }

Example (create an index on the 'emp_no' field):

   var result = db.create_index("company.employee", {emp_no: 1}, "emp_no_index",
                                "MONGO_INDEX_UNIQUE, MONGO_INDEX_DROP_DUPS");

Invoke a MongoDB Command

Synchronous:

   var result = db.command(<database>, <command>);

Asynchronous:

   db.command(<database>, <command>, callback(<error>, <result>));

The Result Object will depend on the nature of the Command invoked. The result is always expressed as a JSON Document.

Example (Obtain a list of all Commands):

   var result = db.command("company", {listCommands : ""});

Example (Get the build information for this MongoDB installation):

   var result = db.command("company", {buildInfo : ""});

Example (Get information about the host):

   var result = db.command("company", {hostInfo : ""});

Example (Get a list of databases):

   var result = db.command("admin", {listDatabases : 1});

Example: (Get statistics for a the 'company' Database):

   var result = db.command("company", {dbStats : 1});

Example (Get statistics for the 'admin' Database):

   var result = db.command("admin", {dbStats : 1});

Example (Return the number of documents in the 'employee' Collection):

   var result = db.command("company", {count: "employee"});

Example (Get statistics for the 'person' Collection):

   var result = db.command("company", {collStats : "employee"});

Using Node.js/V8 worker threads

mongo-dbx functionality can now be used with Node.js/V8 worker threads. This enhancement is available with Node.js v12 (and later).

The following scheme illustrates how mongo-dbx should be used in threaded Node.js applications.

   const { Worker, isMainThread, parentPort, threadId } = require('worker_threads');

   if (isMainThread) {
      // start the threads
      const worker1 = new Worker(__filename);
      const worker2 = new Worker(__filename);

      // process messages received from threads
      worker1.on('message', (message) => {
         console.log(message);
      });
      worker2.on('message', (message) => {
         console.log(message);
      });
   } else {
      var mongodb = require('mongo-dbx');
      var db = new mongodb.server();
      var result = db.open({address: <server>, port: <port>});;

      // do some work

      var result = db.close();
      // tell the parent that we're done
      parentPort.postMessage("threadId=" + threadId + " Done");
   }

License

http://www.mgateway.com
Email: cmunt@mgateway.com

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

  http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Release Notes

v1.2.10 (19 December 2016)

Initial Release

v1.3.11 (22 August 2019)

Support for Node.js v8, v10 and v12.

v1.3.12 (12 September 2019)

Internal changes to replace V8/Node.js API functionality that was deprecated in Node.js v12.

v1.4.13 (6 May 2020)

Verify that mongo-dbx will build and work with Node.js v14.x.x.
Introduce support for Node.js/V8 worker threads (for Node.js v12.x.x. and later). * See the section on 'Using Node.js/V8 worker threads'.

v1.4.14 (28 April 2021)

Verify that mongo-dbx will build and work with Node.js v16.x.x.
A number of faults related to the use of mongo-dbx functionality in Node.js/v8 worker threads have been corrected. In particular, it was noticed that callback functions were not being fired correctly for some asynchronous invocations of mongo-dbx methods.